The sequence of biosynthesis of the 30 S subunit can be represented as follows: 16 S precursor rRNA yields 21 S particle yields 26-28 S particle; precursor 30 S yields mature 30 S subunit. We are proposing to analyze the RNA minor base and protein compositions of these intermediates. This will be carried out by isolating these intermediates which could be accumulated by various cold sensitive sad mutants. In addition, several ribosomal proteins are found to be methylated. Thus it will be of importance to analyze the nature and stoichiometry of the methylated amino acids from these proteins.